Development of a new 3-dimensional scintillating detector for patient treatment quality control in pencil beam scanning proton therapy

In this work, we developed a three-dimensional (3D) scintillation system, whose fast response and high sensitivity allow the measurement of pencil beam (PB) characteristics (position, energy and intensity in terms of monitor units - MU) for pencil beam scanning proton therapy. The system consists of a 10 x 10 x 10 cm(3) scintillator cube that produces visible light when irradiated with PBs. A high-speed camera records the scintillation distribution and a mirror positioned at 45 degrees to the cube allows visualization of two orthogonal faces of the cube. The measurements demonstrated the ability of our system to measure beam characteristics for intensities as low as 2 center dot 10(-3) MU in a single irradiation. Standard deviations of less than 300 mu m were found for the X and Y PB positions, of approximately 150 keV for energy and of less than 5 center dot 10(-3) MU for intensity. These measurements were then successfully used to verify the compliance of the PBs delivery with the treatment plan, thus making our system a fast and efficient verification tool.